This invention is directed to a portable liquid pump.
The pump according to this invention is especially useful for emptying drums, say 55 gallon drums, filled with chemical solutions, plating solutions, and the like.
A feature of the pump is a neutral pressure zone at the bottom of the pump shaft and just above the impeller. This zone makes fragile and expensive seals about the drive shaft unnecessary. The need for complex mechanical and lip seals about the drive shaft is reduced because corrosive liquids are prevented from reaching the motor.
The entire pump is versatile having the capability of pumping liquids with densities up to at least 1.8 specific gravity and with viscosities up to at least 600 cps (centipoise).
U.S. Pat. No. 4,627,790 discloses a unique air seal for axial flow pumps. However, some applications cannot tolerate the entrainment of air in the liquids being pumped. U.S. Pat. No. 3,767,321 teaches an axial flow pump wherein an auxiliary impeller acts upon the liquid surrounding the drive shaft to balance the upward pressure created by the main impeller.